1. Field of the Invention
The present invention relates to sample information obtaining apparatuses and sample information obtaining methods for obtaining information about a sample by, for example, analyzing properties of the sample and performing imaging of the sample, using electromagnetic waves. In particular, the present invention relates to an apparatus and method for, for example, analyzing properties of a sample and performing imaging of the sample using high frequency electromagnetic waves in a millimeter to terahertz wave range.
2. Description of the Related Art
Recently, there have been developed nondestructive testing techniques using high frequency electromagnetic waves with frequencies in a millimeter to terahertz wave range (30 gigahertz (GHz) to 30 terahertz (Thz)). Such high frequency electromagnetic waves are referred to as terahertz waves in the present specification. Absorption lines of various materials, including biomolecules, are known to be present in terahertz waves. Examples of expected applications of the above-described frequency range include an imaging technique for performing a safe fluoroscopic examination as an alternative to an X-ray fluoroscopic examination; a spectroscopic technique for obtaining, for example, absorption spectra and complex permittivity of materials to examine molecular binding states and the like; an analyzing technique for analyzing biomolecules; and a technique for evaluating carrier concentrations and mobility.
Examples of such analyzing methods include a method for detecting a terahertz wave transmitted through test material (i.e., sample) and a method for detecting a terahertz wave reflected from a sample. From these detecting methods, an appropriate method is selected according to the type of properties the measurer wants to obtain. Conventionally, since these detecting methods often involve different optical arrangements, different apparatuses are developed for the respective methods. On the other hand, there is disclosed a technique in which each detecting method is performed by switching between optical systems in an apparatus whose entire structure is enclosed in a single housing (Japanese Patent Laid-Open No. 2004-191302).
This known technique provides a sample information obtaining apparatus including different optical systems for transmittance detection and reflectance detection. Since switching between these optical systems is performed to implement different detecting methods, a sample needs to be placed at a predetermined position appropriate for the detecting method to be implemented. Therefore, when both transmittance detection and reflectance detection are to be performed on one and the same sample, a time difference is made between measurements. For example, when a measurement for reflectance detection is to be performed after the completion of a measurement for transmittance detection, switching from one optical system to another is required and further, a sample needs to be moved from one position to another, accordingly. This takes a relatively long time to obtain information about the sample, and involves a relatively complex configuration of the apparatus.